The main objective of this research proposal is to elucidate mechanisms of information transfer by vertebrate olfactory receptors. The receptors are bipolar neurons, and share certain functional similarities with other primary sensory neurons. Axonal, somatic and dendritic spikes will be recorded extracellularly from individual olfactory receptors. The spikes are generated by an initial event that is extra-cellularly recorded as a summated receptor potential called the electro-olfactogram (EOG). There is little agreement among olfactory physiologists concerning the mechanisms underlying generation of this voltage transient. Hence, the aim of the proposed research is to thoroughly investigate and characterize this initial electrical event triggered by the stimulus, and which in turn activates the spike generating mechanisms. To do so, pharmacological techniques will be used to investigate the receptor potential in isolation from the spike generating mechanism. Responses to orthodromic chemical and antidromic electrical stimulation will be studied. Step intraepithelial electrode penetrations coupled with a laminar profile analysis of the voltage transients will be aimed at revealing the electrogenic source(s) of the receptor potential.